Wedge-shaped wall-diamond lattice structure surface and application thereof

Abstract

The invention discloses a wedge-shaped wall-rhombus lattice structure surface and application thereof. A plurality of rhombus lattice structures are arranged on the surface of a base material in a staggered array mode. The rhombic lattice structure is enclosed by a wedge-shaped bulge structure; wedge-shaped bulge structures are arranged in the rhombic lattice structures along short diagonals; the side of the acute angle in the diamond lattice structure is a convergence end, and wettability differentiated patterns are arranged on the surface of the base material at the convergence end; and except for the wettability differentiation patterns, the base material and the wedge-shaped bulge structures are hydrophobic. The wedge-shaped wall-rhombus lattice structure surface is designed by adopting the bionic principle, the conception is novel, the design is ingenious, and the structure is simple; the rapid and frequent nucleation-growth-migration-merging-falling of liquid drops can be effectively promoted, so that the heat transfer performance and stability of bounce condensation are greatly improved; and programmable droplet control and directional transportation without energy input can be realized by changing the wettability and geometric topology of the structure by virtue of a multi-dimensional rectification effect.

Description

Technical Field

[0001] The present invention belongs to the field of surface design and gas-liquid phase change heat and mass transfer, and in particular provides a double-gradient graded structure surface for optimizing bouncing condensation heat transfer, and specifically relates to a bionic wedge-shaped wall-diamond lattice structure based on the beak of a shorebird, the veins of a foxtail grass, and the skin of a desert beetle, and its application in droplet rectification. Background Art

[0002] Steam condensation is a ubiquitous energy transfer process in nature and is widely used in many industrial fields such as energy management, seawater desalination and power generation. Improving the heat transfer performance of condensation is crucial to energy saving and consumption reduction in life and industrial production processes. It is well known that droplet condensation has a higher heat transfer coefficient than film condensation, and the development of superhydrophobic micro-nanostructure preparation technology has enabled the new bouncing condensation mode to stand out. With the merging and self-bouncing effect of droplets, the heat transfer coefficient of bouncing condensation is nearly doubled compared to droplet condensation. However, the bouncing condensation mode will become unstable and fail as the wall supercooling increases, resulting in deterioration of heat transfer performance.

[0003] To address this bottleneck, researchers proposed to slow down the failure of bounce condensation by preparing micro / nanostructured superwetting surfaces. However, the current scheme still fails to achieve systematic regulation of the entire life cycle of condensed droplets, and it is difficult to ensure the stable operation of bounce condensation under a large supercooling range. In addition, the process of the surface structure involved is relatively complex, and the controllability of the preparation is poor. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention is based on bionics and draws on the liquid directional transport function of the beak structure of shorebirds, the droplet manipulation function of the main veins of Setaria viridis, and the water collection function of the wettability differentiated pattern on the skin of the Namib desert beetle. A wedge-shaped wall-diamond lattice structure surface is designed, which ensures that the condensed droplets continuously and effectively jump off the surface through the multi-dimensional rectification effect, thereby achieving stable and efficient bouncing condensation.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A wedge-shaped wall-diamond lattice structure surface, comprising:

[0007] Base material;

[0008] Arrange a plurality of rhombus lattice structures in a staggered array on the surface of the substrate;

[0009] The rhombus lattice structure is surrounded by four wedge-shaped protruding structures; one set of diagonals in the rhombus lattice structure is an acute angle, and a wedge-shaped protruding structure is arranged along the short diagonal line opposite to the acute angle;

[0010] The side where the acute angle of the rhombus lattice structure is located is a converging end, and a wettability differentiation pattern is arranged on the surface of the substrate at the converging end; except for the wettability differentiation pattern, the substrate and the wedge-shaped protruding structure are both hydrophobic.

[0011] Furthermore, the wettability differential pattern is triangular or fan-shaped and is modified to be hydrophilic with a wetting angle of less than 70°.

[0012] Furthermore, the length of the wettability differentiation pattern is one tenth of the length of the long diagonal line D1 of the rhombus lattice structure.

[0013] Furthermore, the substrate and the wedge-shaped protrusion structure except the wettability differential pattern are all super-hydrophobic with a wetting angle greater than 130°.

[0014] Furthermore, the cross section of the wedge-shaped protrusion structure is a triangle, the width of the base is W, the height H is one to two times of W, and the value range of the width W is: 5μm to 10μm.

[0015] Furthermore, the length L of the side of the rhombus lattice structure is five to ten times the width W of the bottom side of the wedge-shaped protrusion structure.

[0016] Furthermore, the angle α of the acute angle in the rhombus lattice structure is less than 60°.

[0017] Furthermore, the angle α of the acute angle in the rhombus lattice structure is 20 to 40 degrees. A method for preparing a wedge-shaped wall-rhombus lattice structure surface, comprising: preparing a rhombus lattice structure arranged in a staggered array on a substrate; preparing a super-hydrophobic coating on the surface of the substrate and the rhombus lattice structure; and removing the super-hydrophobic coating at the wettability differential pattern to obtain hydrophilicity.

[0018] The invention discloses an application of a wedge-wall-diamond lattice structure surface for heat dissipation of electronic devices and programmable droplet manipulation technology based on a condensation process.

[0019] The beneficial effects of the present invention are:

[0020] (1) In this design, the hydrophilic triangular or fan-shaped patterns act as nucleation sites to precisely control the formation of droplets at two opposite acute-angle vertices in the rhombus lattice structure, that is, at the converging end, so that the overall distribution of the condensed droplets has obvious spatial regularity.

[0021] (2) In this design, the framework structure of the rhombus lattice can ensure the size consistency of the droplets during growth. At the same time, without any external energy input, the generated Laplace pressure gradient is used to drive the droplets to migrate from the converging end to the center of the lattice. The programmable control of this directional self-transport behavior can be achieved by changing the wettability and geometric topological parameters of the rhombus lattice.

[0022] (3) In this design, the droplets will actively seek to merge with each other through spontaneous migration, and the size deviation before merging will be maintained in a low range, which will greatly increase the triggering probability of merging self-bouncing behavior. In addition, the wedge-shaped protrusion structure in the center of the lattice will also improve the energy conversion efficiency of merging self-bouncing.

[0023] (4) This scheme has a clear design concept, simple structure, easy manufacturing, high controllability, and potential for large-scale industrial application. The proposed wedge-shaped wall-diamond lattice structure surface can not only optimize the condensation heat transfer performance and stability, but also serve as a droplet rectifier, achieving long-distance, fast, and programmable droplet directional transport by applying multi-dimensional rectification effects in the in-plane and out-of-plane directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1a is a side view and 1b is a top view of the wedge-shaped wall-diamond lattice structure surface of the present invention.

[0025] Figure 2 It is a structural diagram of the rhombus lattice structure of the present invention.

[0026] Figure 3 Schematic diagram of the multi-dimensional droplet rectification effect of the wedge-shaped wall-diamond lattice structure surface of the present invention.

[0027] Figure 4 4a is a schematic diagram of the effect of the conventional structure surface, and 4b is a schematic diagram of the effect of the structure surface of the present invention.

[0028] Figure 5 5a is a diagram showing the improvement effect of the wedge-shaped wall-diamond lattice structure surface on the surface heat transfer coefficient during condensation compared with the conventional structure surface, and 5b is a diagram showing the improvement effect of the conventional structure, and FIG. 5b is a diagram showing the improvement effect of the structure of the present invention.

[0029] In the figure, 1. substrate, 2. diamond lattice structure, 3. wedge-shaped protrusion structure, 4. wettability differentiation pattern. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be described in a systematic, complete and detailed manner in combination with the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] like Figure 1 and Figure 2As shown in the figure, the present invention provides a surface of a wedge-shaped wall-rhombic lattice structure, including a substrate 1, a rhombic lattice structure 2, a wedge-shaped convex structure 3, and a wettability differentiation pattern 4. Specifically as follows:

[0032] The substrate 1 is a rectangular flat plate structure, which is used to provide bearing and support and conduct heat transfer.

[0033] On any one side surface of the substrate 1, the rhombic lattice structure 2 is surrounded by the wedge-shaped convex structure 3 as the side. Adjacent rhombic lattice structures 2 share the same wedge-shaped convex structure 3. Therefore, the rhombic lattice structures 2 on the substrate 1 are arranged in a staggered array.

[0034] In the rhombic lattice structure 2, one set of opposite angles is acute, and the other set of opposite angles is obtuse. Along the diagonal line at the obtuse angle, another wedge-shaped convex structure 3 is provided. The rhombic lattice structure 2 is evenly divided into two acute triangle regions by the wedge-shaped convex structure 3 at this diagonal line.

[0035] The side where the acute angle is located in the rhombic lattice structure 2 is the converging end, and the wettability differentiation pattern 4 is arranged on the surface of the substrate 1 at the converging end.

[0036] In this embodiment, the wettability differentiation pattern 4 is triangular and is modified to be hydrophilic with a wetting angle less than 70°. The length of this triangular pattern is one-tenth of the length of the long diagonal D1 of the rhombic lattice structure 2. All regions in the rhombic lattice structure 2 except the wettability differentiation pattern 4 are modified to be superhydrophobic with a wetting angle greater than 130°.

[0037] In this embodiment, the entire substrate 1 and the wedge-shaped convex structure 3 are both hydrophobic.

[0038] In this embodiment, the bottom width of the wedge-shaped convex structure 3 is W, and the height H is one to two times of W; the size of W is generally taken as 5μm < W < 10μm.

[0039] In this embodiment, the length L of the side of the rhombic lattice structure 2 is five to ten times of W; the sizes of the long diagonal D1 and the short diagonal D2 of the rhombic lattice structure 2 are in the ranges of 50μm < D1 < 200μm and 10μm < D2 < 50μm respectively.

[0040] In this embodiment, the thickness T size of the substrate 1 is in the range of 500μm to 3mm. The substrate 1 can be made of a metal material with a high thermal conductivity coefficient or polymer materials such as silicon, glass, and polydimethylsiloxane (PDMS) suitable for microfluidic technology.

[0041] In this embodiment, the angle α of the acute angle in the rhombic lattice structure 2 is less than 60°, and the preferred value range is: 20° < α < 40°.

[0042] In this embodiment, the surface structure can be prepared by 3D printing and femtosecond laser technology. The hydrophobicity of the surface can be modified by vapor deposition or ultrasonic spraying, and the hydrophilic area can be prepared by femtosecond laser processing with mask pattern.

[0043] In this embodiment, the wedge-shaped wall-diamond lattice structure surface designed by the present invention is prepared based on the integration of single crystal silicon wafers. The specific preparation steps are as follows:

[0044] A 500 μm thick silicon wafer was cut into square samples with a side length of 2 cm, a diamond lattice photoresist pattern with a set size was coated on the sample silicon wafer, a wet etching process was used for photolithography to prepare a silicon wafer with a diamond lattice array structure, and the excess photoresist was washed away with acetone solution.

[0045] Next, the sample was rinsed with acetone, ethanol and deionized water, and the surface was blown dry with nitrogen. It was immersed in a commercial super-hydrophobic coating solution for 10 min. The sample was then taken out and placed in an air drying oven at 120 °C for 30 min to cure the super-hydrophobic coating. The above immersion-drying process was repeated three times.

[0046] Finally, set the laser energy density to 0.15 J / cm 2 , with a scanning speed of 4 mm / s. Based on the femtosecond laser double-beam interference technology and combined with the cylindrical lens line scanning technology, the super-hydrophobic coating is removed in the converging end area of ​​the diamond lattice structure and a triangular pattern is processed. The pattern is hydrophilic due to the exposed silicon substrate.

[0047] The frame of the rhombus lattice structure 2 is composed of a wedge-shaped protruding structure 3, the size of which can be adjusted by controlling the etching time, and the corresponding bottom width W is about 5 μm, the height H is about 10 μm, and the length L is about 50 μm.

[0048] The opening angle α of the converging end of the rhombus lattice structure 2 is 25°, the lengths D1 and D2 of the long diagonal and the short diagonal are approximately 98 μm and 22 μm respectively, and the length of the triangle pattern at the converging end is one fifth of the length of the half diagonal of the lattice, which is approximately 10 μm.

[0049] like Figure 3As shown, when the wedge-shaped wall-diamond lattice structure surface is placed in a steam condensation environment, water vapor will preferentially nucleate at the convergent end of the diamond lattice, and the resulting condensed droplets will present a regular spatial distribution. Under the physical constraints of the lattice structure framework, the condensed droplets will undergo asymmetric deformation front and back due to extrusion during the growth process, and the resulting Laplace pressure difference will drive them to move from the convergent end to the center of the lattice. When both droplets migrate to the center of the lattice and actively seek to merge with the adjacent droplets (in-plane rectification effect), they will efficiently jump off the surface under the impetus of the wedge-shaped protrusion structure at the center (out-of-plane rectification effect).

[0050] like Figure 4 As shown in FIG. 1 , under the effect of the multi-dimensional rectification effect, the droplets on the wedge-shaped wall-diamond lattice structure surface will be more efficiently detached and refreshed more frequently than those on the conventional structure surface, so the size of the residual droplets on the surface will be constrained within a certain range. Figure 5 As shown, based on the rapid and frequent nucleation-growth-migration-merger-shedding behavior of condensed droplets, the condensation heat transfer coefficient of the wedge-wall-diamond lattice structure surface is greatly improved compared with the conventional structure surface.

[0051] The present invention is based on the concept of bionics. With the help of the wedge-shaped protrusions that imitate leaf veins, a super-hydrophobic rhombus lattice that imitates the structure of a bird's beak is formed. The rhombus lattice structure is laid out in a tightly staggered form, and its obtuse vertices are connected by wedge-shaped protrusion structures, while the converging ends where the acute vertices are located are modified by hydrophilic triangles or fan-shaped patterns. This surface can ensure that droplets are formed at the converging ends of the lattice structure in the condensation process, showing a spatially regular nucleation distribution; then asymmetric Laplace pressure is provided to drive the droplets to spontaneously migrate from the converging ends to the lattice center and actively seek to merge with adjacent droplets; finally, the wedge-shaped protrusion structure at the center of the lattice will prompt the merged droplets to quickly and efficiently jump off the surface. The present invention has a novel concept, an ingenious design and a simple structure, and can effectively promote the rapid and frequent nucleation-growth-migration-merger-and-shedding of droplets, thereby greatly improving the heat transfer performance and stability of bouncing condensation; it can also make use of the multi-dimensional rectification effect to achieve programmable droplet manipulation and directional transport without energy input by changing the wettability and geometric topology of the structure; the present invention has a novel concept, an ingenious design and a simple structure, and can effectively promote the rapid and frequent nucleation-growth-migration-merger-and-shedding of droplets, thereby greatly improving the heat transfer performance and stability of bouncing condensation; it can also make use of the multi-dimensional rectification effect within and outside the plane to achieve programmable droplet manipulation and directional transport without energy input.

[0052] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A wedge-shaped wall-diamond lattice structure surface, characterized in that: include: Substrate (1); Arranging a plurality of rhombus lattice structures (2) in a staggered array on the surface of the substrate (1); The rhombus lattice structure (2) is surrounded by four wedge-shaped protruding structures (3); one set of diagonals in the rhombus lattice structure (2) is an acute angle, and a wedge-shaped protruding structure (3) is arranged along the short diagonal line opposite to the acute angle; The side where the acute angle of the rhombus lattice structure (2) is located is a convergence end, and a wettability differentiation pattern (4) is arranged on the surface of the substrate (1) at the convergence end; except for the wettability differentiation pattern (4), the substrate (1) and the wedge-shaped protrusion structure (3) are both hydrophobic.

2. The wedge-shaped wall-diamond lattice structure surface according to claim 1, characterized in that: The wettability differential pattern (4) is in the shape of a triangle or a fan, and is modified to be hydrophilic with a wetting angle of less than 70°.

3. The wedge-shaped wall-diamond lattice structure surface according to claim 1, characterized in that: The length of the wettability difference pattern (4) is one tenth of the length of the long diagonal line D1 of the rhombus lattice structure (2).

4. The wedge-shaped wall-diamond lattice structure surface according to claim 1, characterized in that: The substrate (1) and the wedge-shaped protruding structure (3) except the wettability differential pattern (4) are all super-hydrophobic with a wetting angle greater than 130°.

5. The wedge-shaped wall-diamond lattice structure surface according to claim 1, characterized in that: The cross section of the wedge-shaped protrusion structure (3) is a triangle, the width of its base is W, the height H is one to two times of W, and the value range of the width W is: 5μm to 10μm.

6. The wedge-shaped wall-diamond lattice structure surface according to claim 1, characterized in that: The length L of the side of the rhombus lattice structure (2) is five to ten times the width W of the base of the wedge-shaped protrusion structure (3).

7. The wedge-shaped wall-diamond lattice structure surface according to claim 1, characterized in that: The angle α of the acute angle in the rhombohedral lattice structure (2) is less than 60°.

8. The wedge-shaped wall-diamond lattice structure surface according to claim 1, characterized in that: The acute angle α in the rhombus lattice structure (2) is as small as 20 to 40°.

9. A method for preparing a wedge-shaped wall-diamond lattice structure surface, characterized in that: Integrally preparing a rhombus lattice structure (2) arranged in a staggered array on a substrate (1); and preparing a super hydrophobic coating on the surface of the substrate (1) and the rhombus lattice structure (2); The super-hydrophobic coating is removed at the wettability differential pattern (4) to obtain hydrophilicity, thereby obtaining a wedge-shaped wall-diamond lattice structure surface as claimed in claim 1.

10. An application of a wedge-shaped wall-diamond lattice structure surface, characterized in that: The wedge-shaped wall-diamond lattice structure surface as described in claim 1 is used for heat dissipation of electronic devices and programmable droplet manipulation technology based on the condensation process.

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